Method and apparatus for fracturing a subsurface formation



July 10, 1956 L. F. BONNER METHOD AND APPARATUS FOR FRACTURING A SUBSURFACE FORMATION FLUID 2 Sheets-Sheet I.

" swivsl. JOINTED CONDUIT FIG I FRACTURING ROTARY TABLE "III DERRICK FLOOR FLUID RETURN LINE FIG. 6.

PACKER INVENTOR.

Louis F. Bonner,

AT ORN July 10, 1956 F. BONNER METHOD AND APPARATUS FOR FRACTURING A SUBSURFACE FORMATION Filed May 11, 1953 2 Sheets-Sheet 2 FIG.2.

FIG. 5-

FTIG. 4.

INVENTOR. Louis F. Bonner,

ATTOR nited States Fatent 6 METHOD AND APPARATUS FOR FRACTURING A SUBSURFACE FORMATION Louis F. Bonner, Houston, Tex., assignor, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, N. 1., a corporation of Delaware Application May 11, 1953, Serial No. 354,344

15 Claims. (Cl. 166-42) The present invention is directed to increasing the permeability of subsurface earth formations. More particularly, the invention is directed to fracturing of subsurface earth formations. In its more specific aspects, the invention is directed to a method for increasing the permeability of a low permeability subsurface earth formation whereby valuable fluids in the low permeability formation may be recovered.

The present invention may be briefly described as a method for increasing the permeability of a low permeability subsurface earth formation in a well bore penetrating said formation which comprises establishing a first path of flow from the earths surface to the formation. A portion of the well bore penetrating the formation is isolated from upper portions of the well bore. A second path of flow from the earths surface is established to a point above the isolated portion and thence to the earths surface. A fracturing liquid is then flowed under pressure down the well bore along the second path of flow. Once the flow has been established, it is suddenly interrupted along the second path of flow, and the flow is directed along the first path of flow into contact with the formation for a period of time sufficient to utilize the energy in the flowing liquid to cause fractures in the formation and increase the permeability thereof. After the fractures have been formed, valuable fluids, such as oil and/ or gas and the like, may be produced from the originally low permeability formation which has had its permeability increased.

The invention is also directed to apparatus for fracturing subsurface earth formations which is adapted to be connected to a lower end of a pipe such as a tubing string in a well bore. The apparatus comprises, in combination, a valve which is connected to the lower end of the pipe string, which has at least a port communicating the interior of the valve with an exterior surface of the valve. The valve is provided with means for closing and opening the port. A pipe extension member is connected to the lower end of the valve. The pipe extension member has a check valve arranged in a lower end of the pipe extension member to resist backflow into the apparatus. The pipe extension member carries a packer which is employed to isolate the earth formation from the upper portion of the well bore.

The valve of my apparatus may embody as a closing means a sleeve slidably arranged on the valve which is operated by lowering and raising the pipe string to which the valve and pipe extension member is connected.

The closing means may be a piston having a central bore slidably arranged in the valve to close and open the bore on movement of the pipe either rotatably or vertically.

The closing means may also be a spring-biased piston having a central bore which is operative on flow of fluid through the valve from the earths surface.

It is further contemplated that the valve employed in my apparatus may be a wire line removable valve of a type operable by fluid flow in which the wire line re- 2,753,94fi Patented July 10, 1956 movable valve embodies ports in the pipe string and a removable member comprising a mandrel having a fishing spear and the like on an upper end and having a spring-biased piston slidably arranged on the mandrel.

The invention will be further illustrated by reference to the drawing, in which Fig. 1 shows an arrangement of my apparatus in a well bore;

Fig. 2 is a sectional view of a fluid operated valve suitable for use in my invention;

Fig. 3 is a sectional view embodying a wire line removable fluid valve which may suitably be employed;

Fig. 4 is a sectional view of a slidable valve operable by vertical movement of the pipe string;

Fig. 5 is a sectional view of a slidable valve operable by rotatable movement of the pipe string;

Fig. 6 is a sectional view of a slidable valve as illustrated in Fig. 1; and

Fig. 7 is an enlarged sectional view of the check valve of Fig. 1.

Referring now to the drawing, numeral 11 designates a cased well bore in which is arranged a pipe string 12 provided with a slidable valve 13 having release ports 14. The casing 11 extends from the earths surface to a point just above a producing formation 15 which is penetrated by the well bore 16 which has not been cased. The pipe string 12 is provided with an extension member 17 which carries a packer 18 which is set in the upper portion of the producing formation 15. The lower or open end 19 of the extension member 17 is provided with a check valve. 20 to resist backfiow into the pipe string 12. The well bore extends to the earths surface 21, and the casing 11 terminates at its upper end below the derrick floor 22 and is closed by cap 11, the pipe string 12 being arranged in a rotary table 23. Connected to the pipe string 12 is a flexible or swivel jointed conduit 24 which connects into a pump 25, which is in turn connected to the casing 11 by a conduit 26 to allow flow from the annulus A between the outer surface of the pipe string 12 and the inner surface of the casing 11. The pipe string 12 may be moved vertically by means of a wire line or suitable hoist 27 connected to a hoisting machine, not shown. The wire line 27 is connected to the pipe string 12 by suitable well known connecting devices indicated generally by 28 and, by means of the rotary table 23 which is connected by means not shown to suitable power equipment, the pipe may also be moved rotatably in the pipe casing 11.

Referring now to Fig. 2, a modification of a valve is disclosed which may be used in lieu of slide valve 13. The valve of Fig. 2 is indicated generally by the numeral 40 and comprises a pipe section 41 provided with ports 42. The pipe section 41 may be connected into the pipe string 12 by means of a suitable threaded connecting means 43.

Arranged in the pipe section 41 embodying the valve of the presentinvention is a piston member 44 embodying a longitudinal member 45 provided with a central bore 46 which allows flow of fluid from the pipe string through the valve 40. Arranged in the pipe section 41 is a bumper or suitable member 47 which supports the member 45. Arranged between the bumper 47 and the piston 44 is a biasing means 48 which suitably may be a helical coil spring. The longitudinal member 45 is provided with ports 49 which allow fluid flow from the central passageway 46 and through the ports 42. The whole assembly is held together by means of a threaded retaining nut 50 which is threadably engaged with the member 45 and holds it in place against the bumper 47 and serves to restrain the spring 48. The bumper sub 47 is threaded into a pipe extension member 51 which carries the packer, as illustrated in Fig. 1.

In the apparatus of Fig. 3, identical numerals are employed to designate identical parts as to Fig. 2. Thus the valve is indicated generally as 40, and a pipe section 41 is provided with ports 42. In this particular embodiment of my invention, the movable member of the valve is retrievable or may be located by means of a wire line. To this end, a mandrel is provided having a cage and fishing spear 61 on the upper end thereof and having a guide point and a cage 62 on a lower end thereof. The mandrel 60 is positioned by a bumper or restraining means 63. Arranged above the bumper 63 is an annular plate 65. Arranged adjacent the upper end of the mandrel 60 is a piston 66 which is slidably arranged on the mandrel 60. Between the piston 66 and the annular plate is a biasing means 67 which may be a helical coil spring which is held in place by a threaded retaining nut 64. The biasing means 67 urges the piston 66 upwardly. The mandrel 60 defines a central passageway 68 which allows flow through the pipe section 41 through the openings 69 and outwardly therefrom through the openings 70 in the guide point 62. The bumper 63 is threaded into a pipe extension member 72 which carries a packer, as illustrated in Fig. l. The movable member may then be lowered by means of a wire line to the desired point.

In the embodiment of Fig. 4, a casing 11 has arranged therein a pipe which is provided with ports 81. The lower end of the pipe 80 is provided with an annular sleeve 82 which is threadably connected thereto by mating threads 83. Slidably arranged in the pipe 80 is a piston member 84 which is provided with a central passageway 85. The sleeve and the piston member 84 define annular space 86 by way of which fluid may escape. The piston 84 has an extension member 87 which is connected into a plug 88, which in turn is connected to a pipe extension member 89 by mating threads 90. The pipe extension member 89 carries a packer 91 to seal off an annulus 92 between the extension member 89 and the pipe 80 with the casing 11.

Referring now to Fig. 5, identical numerals will designate identical parts as to Fig. 4. It will be seen that a pipe 80 is provided with ports 81, and arranged in the pipe 80 is a slidable piston 84 having a central passageway 85. In this modification of my invention, the lower end of the pipe 80 is provided with cam surfaces 100, and the upper end of the pipe extension member 89 is provided with cam surfaces 101 to correspond with the cam surfaces 100. The extension member 87 is connected to a plug 88, which in turn is connected by mating threads to the pipe extension 89. The pipe extension 89 carries a packer 91 as in Fig. 4.

Referring now to Fig. 6, a pipe tubing 12 has attached to it a slidable sleeve 13. The slidable sleeve 13 fits over a valve body 113 and is provided with a suitable sealing means such as an O-ring 114 arranged in a recess 114a.

The valve body 113 is provided with a plurality of ports 14 which allows communication with the central passageway 116 and the interior of pipe tubing 12. The lower end of the valve body 113 serves as a pipe extension member 17 which carries a packer 18 to allow the lower end of the bore hole to be isolated from an upper end.

The sleeve 112 is constructed of two parts 119 and 120. Part 119 is attached to the pipe 110, and part 120 is threadably attached to part 119. Part 120 is provided with an internal shoulder 121 which serves as a stop for limiting upward movement of sleeve 112. Valve body 113 has a shoulder 122, which limits upward travel of sleeve 112 by engagement with stop 121.

With respect to Fig. 7, the check valve 20 is arranged in the extension member 17 adjacent the lower open end 19 and is comprised of a seating member for seating of the valve member 131 thereon. The valve member 131 is provided with a seal 132 and has a stem or guide member 133 arranged in a spider 134. The valve memher 131 is biased into seating engagement with the seating member 130 by a biasing means, such as a helical coil spring 135, which normally holds the valve member 131 in closed position. The check valve 20 is opened by a predetermined pressure overcoming or compressing the spring 135.

The apparatus of my invention is employed in the following manner to obtain production from low permeability producing formations and to increase the permeability thereof.

Referring now to Fig. 1, the casing 11 has been .ccmented securely in the well bore by means of cement, indicated generally as C. Thereafter the pipe 12 in which is arranged a valve, such as 13, shown in more detail in Fig. 6, is lowered into the well. The valve has connected to its lower end a pipe 17 which has a check valve arranged adjacent the lower end 19 of the pipe extension 17. Carried on the pipe 17 is a packer which is set by suitable means well known to the art at a point in or at the top of the formation 15.

Fracturing fluid is drawn into the pump 25 by means of a conduit 130 controlled by valve 131 from a source not shown which may be a suitable tank. The fracturing fluid is flowed down through the pipe 12 and out through ports 14 since the packer 18 has been set and since the check valve is of the type to restrain flow and to be overcome by a designated pressure. The flow is down the pipe 12 through the ports 14 and up the annulus A, as indicated by the arrows. Thence the fluid returns by conduit 26 and pump 25 and back down the tubing or pipe 12. After the flow has been established along the path indicated, it is desired to fracture the formation 15; then slide valve 13 may be manipulated by lowering the pipe 12 such that the sleeve 13, as in Fig. 6, will cover the ports shown in Figs. 1 and 6 as 14. This causes the flow to proceed down through the pipe 17 to unseat the check valve 20 and out through the open end 19. The energy contained in the flowing stream is thus exerted suddenly against the formation 15, which is sufficient to cause horizontal and/ or vertical fractures in the formation 15 to increase the permeability thereof. The pipe string 12 may then be raised to open the ports 14 and to allow flow along the path defined by pipe 12 through ports 14, annulus A, conduit 26, pump 25 and conduit 24. The sequence may be repeated by lowering the pipe 12 such that the sleeve 13 again covers the ports 14 to utilize the energy of the moving column against the formation 15.

In the apparatus of Fig. 2, the helical coil spring 48 normally urges the piston or plunger 44 upwardly leaving the port 42 open such that fluid passes from the pipe string to which the valve is connected by connecting means 43 through central passageway 46 and thence through ports 49 and 42 to the annulus A. When the velocity of the fluid flowing down the pipe string increases to a predetermined value, the ports 49 have insutficient flow area to allow the fluid to pass without a build-up in pressure. This causes the plunger or piston 44 to move downwardly, overcoming the tension of spring 48. Thus the plunger or piston 44 then covers the ports 49 and forces the fracturing liquid to pass down the central passageway 46 and thence against the formation 15 described with respect to Fig. 1. The valve 40 remains closed until the flow through check valve 20 drops below a predetermined value. The valve then opens and fluid circulation up the annulus is resumed and the cycle repeated. The time between opening and closing the valve may vary from a fraction of a second to several seconds, say from 0.01 to 20 seconds.

The apparatus of Fig. 3 operates similarly to that of Fig. 2. In this respect, however, the valve may be located by a wire line device connected to the spear 61 such that the device may be lowered to the proper position in the pipe section 41 until it is adjacent the ports 42. Fluid is then pumped down the pipe connected by connecting means 43 and through the valve 40 until the velocity forces the piston 66 to move downwardly on mandrel 60, compressing spring 67 and covering the ports 42. Thus the fluid is forced abruptly through the opening 69 into passageway 68 and thence through opening 70 down into the well bore below the packer and against the formation to be fractured.

The apparatus of Figs. 4 and 5 works in a similar manner. With respect to Fig. 4, the piston member 84 covers the ports 81 by sliding the pipe 80 downwardly, the extension member 87 being only of suflicient length to allow movement of the piston 84 sufiiciently to cover ports 81. This operation may be conducted rapidly to cause a water hammer effect when flow through the ports 81 is interrupted and to cause flow through passageway 85 and thence against the formation, as has been described with respect to Fig. 1.

In the device of Fig. 5, the piston 84 is caused to cover the ports 81 by rotating the pipe 80 with the rotary table 23. This causes the cam surfaces 100 and 101 to open and close the ports 81 vertically by upward and downward movement of the piston 84. This sudden opening and closing of the ports allows the flow to be diverted to the central passageway 85 and against the formation 15, as has been described.

The operation of the device of Fig. 6 has been substantially described with respect to Fig. 1 which employs identical equipment and will not be repeated here in the interest of briefness.

The check valve is opened by a designated pressure compressing the spring 135; on release of pressure by opening port 14, the check valve 20 closes by the action of spring 135.

The present invention utilizes the energy contained in a flowing or pumped stream wherein the flow is suddenly interrupted. In short, I exert a water hammer effect against a low permeability formation such that by means of the energy contained in the stream, I fracture the formation without expenditure of a large amount of pumping energy.

As liquids or fluids suitable for use in fracturing formations having low permeability I may use, in accordance with my invention, oil, water and dilute hydrochoric acid and the like. If acid is used, it may react chemically with the formation to enlarge the fissures thereof while it is being injected into the formation or thereafter. Under some conditions, oil is deemed the most suitable liquid for the purpose, as it does not contaminate oilbearing rock formations as does water, and its viscosity may be easily controlled as by mixing it with suitable soaps, as is well known to those skilled in the art of making oil base driling fluids. In an oil producing formation, liquid can perhaps be removed easier in an aqueous treating or fracturing fluid. In this respect, see The Flow of Homogeneous Fluids Through Porous Media by M. Muskat, copyright 1937, McGraw-Hill Book Company, pages 478-480.

Under some conditions, liquids of very low viscosity may be employed, although it is recognized that if sand or gravel are mixed with the liquid which is forced into the formation by the water hammer effect, the liquid may have a sufliciently high viscosity to suspend the particles of such materials uniformly. Under other conditions, liquid of reasonably high viscosity may be employed, but in no event should the viscosity of the liquid be so high that the formation becomes clogged by the liquid after the formation has been fractured. From the foregoing, it may be seen that I contemplate employing as a fracturing liquid either a hydrocarbon vehicle or an aqueous vehicle. I further contemplate that either the hydrocarbon or aqueous vehicle may contain a propping agent such as sand or gravel, which will serve to maintain the fracture or fissures in the formation in an open condition after the fractures have been formed.

In my invention, after I have fractured the formation by utilizing the apparatus described whereby a water hammer effect is employed, the desirable subsurface fluid in the formation would be allowed to flow under its own pressure from the formation into the well and produced.

It is contemplated and it may be desirable that after the fracturing operation has been conducted, the packers used to isolate the formation may be unseated and retrieved. Packers suitable in the practice of the present invention are well known in the art. A description of a packer which may be employed in my invention may be found on page 2852 of the 1951 Edition of Composite Catalog of Oil Field and Pipe Line Equipment, shown as packer model (3-100.

For the present invention to be effective, it is contemplated that the flow of the fracturing fluid will be interrupted only momentarily, a matter of perhaps 0.01 to 20 seconds such that the water hammer effect may be created. lt is contemplated that the water hammer effect may be exerted against the formation a plurality of times or only once, as is necessary to increase the permeability of a formation to a desired value. Thereafter the formation may be produced after normal clean out operations well known to the art have been performed. It is intended that this invention will include the steps of increasing the permeability of a producing oil formation and then producing said formation.

The fracturing liquid employed may be insuflicient in amount to fill the pipe and the annulus, and it is, therefore, contemplated that a column of mud or water or other liquid may be used to follow the charge of fracturing liquid. Also it is considered that the column of mud or water may be used in the annulus above the packer instead of having the annulus filled with fracturing liquid.

The nature and objects of the present invention having been completely described and illustrated, what I wish to claim as new and useful and to secure by Letters Patent 1. A method for increasing the permeability of a low permeability subsurface earth formation in a well bore penetrating said formation which comprises establishing a first path of flow from the earths surface to said formation, isolating at least a portion of the well bore penetrating said formation from an upper portion of said well bore, establishing a second path of flow from the earths surface to a point above said isolated portion common with said first path of flow and thence to the earths surface, pumping a fracturing liquid under pressure down said well bore along said second path of flow, terminating the flow along said second path of flow, and then pumping said fracturing liquid along said first path of flow into contact with said formation whereby the energy of the pumped liquid is exerted against said formation to fracture same and increase the permeability thereof.

2. A method in accordance with claim 1 in which the fracturing liquid is a hydrocarbon vehicle.

3. A method in accordance with claim 1 in which the fracturing liquid is a hydrocarbon vehicle containing a propping agent.

4. A method in accordance with claim 1 in which the fracturing liquid is an aqueous vehicle.

5. A method for producing a desirable subsurface earth fluid from a low permeability subsurface earth formation in a well bore penetrating said formation which comprises establishing a first path of flow from the earths surface to said formation, isolating at least a portion of the well bore penetrating said formation from the upper portion ofsaid well bore, establishing a second path of flow from the earths surface to a point above said isolated portion common with said first path of flow and thence to the earths surface, pumping a fracturing fluid under pressure down said well bore along said second path of flow, terminating the flow along said second path of flow, pumping said fracturing fluid along said first path of flow into contact with said formation for a period of time in the range from 0.01 to 20 seconds whereby the energy of the pumped liquid is utilized to fracture said formation and 7 increase the permeability thereof, and then recovering the desired earth fluid from said fractured formation.

6. A method in accordance with claim 5 in which the fracturing liquid is a hydrocarbon vehicle.

7. A method in accordance with claim 5 in which the fracturing liquid is a hydrocarbon vehicle containing a propping agent.

8. A method in accordance with claim 5 in which the fracturing liquid is an aqueous vehicle.

9. Apparatus for fracturing a subsurface earth formation which comprises, in combination, a pipe tubing adapted to be arranged in a well bore with its lower end adjacent the formation to befractured and its upper end extending above the earths surface, valve means arranged in said tubing adjacent the lower end of the tubing provided with at least one port communicating the interior of the tubing with the exterior of the tubing, means for opening and closing said port, an upwardly biased check valve in the lower end of the tubing normally closing the lower end of the tubing and openable under a designated pressure for flow downwardly through the tubing, a packer carried by said tubing between said valve means and said check valve for isolating said earth formation from the well bore, conduit means flexibly connected to the upper end of said pipe tubing, and pumping means connected to said conduit means for pumping fracturing fluid to said formation while said valve means and said check valve are alternately opened and closed.

10. Apparatus in accordance with claim 9 in which means are provided for moving said pipe tubing to cover and uncover said port while fracturing fluid is being pumped downwardly through said pipe tubing.

11. Apparatus in accordance with claim 9 in which the closing and opening means is a sleeve slidably arranged on said valve to close and open said port by lowering and raising the pipe.

12. Apparatus in accordance with claim 9 in which the closing and opening means is a piston having a central bore slidably arranged in said valve to close and open said port on movement of the pipe.

13. Apparatus in accordance with claim 9 in which the closing and opening means is a spring biased piston having a central bore slidably arranged in said valve to close and open said port on flow of liquid through the valve.

14. A method for producing a desired subsurface earth fluid from a low permeability subsurface earth formation in a Well bore penetrating said formation which comprises establishing a path of flow from the earths surface to said formation, isolating at least a portion of the well bore penetrating said formation from an upper portion of said well bore, establishing a second path of flow from the earths surface to a point above said isolated portion common with said first path of flow and thence to the earth's surface, pumping a fracturing fluid under pressure down said well bore along said second path of flow, terminating the flow along said second path of flow, pumping said fracturing fluid along said first path of flow into contact with said formation for a period of time in the range from 0.01 to 20 seconds whereby the energy of the pumped liquid utilized to fracture said formation and increase the permeability thereof, removing fracturing fluid from said formation and said first path of flow, and obtaining the desired earth fluids from said fractured formation.

15. A method in accordance with claim 14 in which the earth fluid is a hydrocarbon.

References Cited in the file of this patent UNITED STATES PATENTS 1,778,740 Wightman Oct. 21, 1930 2,129,216 Johnston Sept. 6, 1938 2,235,318 Halliburton Mar. 18, 1941 2,325,264 Merten July 27, 1943 2,355,259 Bancroft et al. Aug. 8, 1944 2,397,473 Crowell Apr. 2, 1946 2,426,164 Breukelman Aug. 26, 1947 

1. A METHOD FOR INCREASING THE PERMEABILITY OF A LOW PERMEABILITY SUBSURFACE EARTH FORMATION IN A WELL BORE PENETRATING SAID FORMATION WHICH COMPRISES ESTABLISHING A FIRST PATH OF FLOW FROM THE EARTH''S SURFACE TO SAID FORMATION, ISOLATING AT LEAST A PORTION OF THE WELL BORE PENETRATING SAID FORMATION FROM AN UPPER PORTION OF SAID WELL BORE, ESTABLISHING A SECOND PATH OF FLOW FROM THE EARTH''S SURFACE TO A POINT ABOVE SAID ISOLATED PORTION COMMON WITH SAID FIRST PATH OF FLOW, TERMINATING FACE, PUMPING A FRACTURING LIQUID UNDER PRESSURE DOWN SAID WELL BORE ALONG SAID SECOND PATH OF FLOW, TERMINATING THE FLOW ALONG SAID SECOND PATH OF FLOW, AND THEN PUMPING SAID FRACTURING LIQUID ALONG SAID FIRST PATH OF FLOW INTO CONTACT WITH SAID FORMATION WHEREBY THE ENERGY OF THE PUMPED LIQUID IS EXERTED AGAINST SAID FORMATION TO FRACTURE SAME AND INCREASE THE PERMEABILITY THEREOF. 